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Lars Stegger

Publications and source records attributed to Lars Stegger.

14 recordsLinked to original sources
PubMed2007

Quantification of left ventricular volumes and ejection fraction from gated 99mTc-MIBI SPECT: validation of an elastic surface model approach in comparison to cardiac magnetic resonance imaging, 4D-MSPECT and QGS.

PURPOSE: The segmentation algorithm ESM based on an elastic surface model was validated for the assessment of left ventricular volumes and ejection fraction from ECG-gated myocardial perfusion SPECT. Additionally, it was compared with the commercially available quantification packages 4D-MSPECT and QGS. Cardiac MRI was used as the reference method. METHODS: SPECT and MRI were performed on 70 consecutive patients with suspected or proven coronary artery disease. End-diastolic (EDV) and end-systolic (ESV) volumes and left ventricular ejection fraction (LVEF) were derived from SPECT studies by using the segmentation algorithms ESM, 4D-MSPECT and QGS and from cardiac MRI. RESULTS: ESM-derived values for EDV and ESV correlated well with those from cardiac MRI (correlation coefficients R=0.90 and R=0.95, respectively), as did the measurements for LVEF (R=0.86). Both EDV and ESV were slightly overestimated for larger ventricles but not for smaller ventricles; LVEF was slightly overestimated irrespective of ventricle size. The above correlation coefficients are comparable to those for the 4D-MSPECT and QGS segmentation algorithms. However, results obtained with the three segmentation algorithms are not interchangeable. CONCLUSION: The ESM algorithm can be used to assess EDV, ESV and LVEF from gated perfusion SPECT images. Overall, the performance was similar to that of 4D-MSPECT and QGS when compared with cardiac MRI. Results obtained with the three tested segmentation methods are not interchangeable, so that the same algorithm should be used for follow-up studies and control subjects.

Adult↗
PubMed2007

Molecular cardiovascular imaging using scintigraphic methods.

Molecular cardiovascular imaging plays an increasingly important role both in basic research and in clinical diagnosis. Scintigraphic methods have long been used to study pathophysiological changes on a cellular and molecular level, and they are likely to remain important molecular imaging modalities in the foreseeable future. This article provides an overview over current developments in cardiovascular molecular imaging using scintigraphic methods. The focus lies on imaging of cardiac innervation, plaque instability, hypoxia and angiogenesis, gene expression and stem and progenitor cell migration and proliferation.

Animals↗
PubMed2006

Unexpected finding of elevated glucose uptake in fibrous dysplasia mimicking malignancy: contradicting metabolism and morphology in combined PET/CT.

Fibrous dysplasia is a common benign disorder of bone in which fibro-osseous tissue replaces bone spongiosa. Lesions have a typical appearance on computed tomography (CT) images and regularly show a markedly increased uptake in bone scintigraphy using (99m)Tc-labelled methylene diphosphonate ((99m)Tc-MDP) as radiotracer. The glucose avidity of these lesions depicted by positron emission tomography (PET) using the radiolabelled glucose derivative (18)F-fluoro-2-deoxy-glucose (FDG) is less well known since FDG-PET does not have a role in the assessment of this disease. However, single cases have been reported in which fibrous dysplasia was present in patients undergoing FDG-PET scanning for oncological reasons, and no significant FDG uptake was observed for lesions identified as fibrous dysplasia. We report on a 24-year-old man with known fibrous dysplasia who underwent combined FDG-PET/CT scanning because of suspected recurrence of testicular cancer. In contrast to prior reports, a markedly elevated uptake of FDG was seen in numerous locations that were identified as fibrous dysplasia by CT. Based on this result, we conclude that fibrous dysplasia may mimick malignancy in FDG-PET and that coregistered CT may help to resolve these equivocal findings.

Adult↗
PubMed2006

Respiratory gating of cardiac PET data in list-mode acquisition.

PURPOSE: Respiratory motion has been identified as a source of artefacts in most medical imaging modalities. This paper reports on respiratory gating as a means to eliminate motion-related inaccuracies in PET imaging. METHODS: Respiratory gating was implemented in list mode with physiological signal recorded every millisecond together with the PET data. Respiration was monitored with an inductive respiration monitor using an elasticised belt around the patient's chest. Simultaneous ECG gating can be maintained independently by encoding ECG trigger signal into the list-mode data. Respiratory gating is performed in an off-line workstation with gating parameters defined retrospectively. The technique was applied on a preliminary set of patient data with C(15)O. RESULTS: Motion was visually observed in the cine displays of the sagittal and coronal views of the reconstructed respiratory gated images. Significant changes in the cranial-caudal position of the heart could be observed. The centroid of the cardiac blood pool showed an excursion of 4.5-16.5 mm (mean 8.5+/-4.8 mm) in the cranial-caudal direction, with more limited excursion of 1.1-7.0 mm (mean 2.5+/-2.2 mm) in the horizontal direction and 1.3-3.7 mm (mean 2.4+/-0.9 mm) in the vertical direction. CONCLUSION: These preliminary data show that the extent of motion involved in respiration is comparable to myocardial wall thickness, and respiratory gating may be considered in order to reduce this effect in the reconstructed images.

Artifacts↗
PubMed2006

Gated listmode acquisition with the quadHIDAC animal PET to image mouse hearts.

PURPOSE: The aim of this study was to develop ECG and respiratory gating in combination with listmode acquisition for the quadHIDAC small-animal PET scanner. METHODS: ECG and respiratory gating was realized with the help of an external trigger device (BioVET) synchronized with the listmode acquisition. Listmode data of a mouse acquisition (injected with 6.5 MBq of 18F-FDG) were sorted according to three different gating definitions: 12 cardiac gates, 8 respiratory gates and a combination of 8 cardiac and 8 respiratory gates. Images were reconstructed with filtered back-projection (ramp filter), and parameters like left ventricular wall thickness (WT), wall-to-wall separation (WS) and blood to myocardium activity ratios (BMR) were calculated. RESULTS: Cardiac gated images show improvement of all parameters (WT 2.6 mm, WS 4.1 mm, BRM 2.3) in diastole compared to ungated images (WT 3.0 mm, WS 3.4 mm, BMR 1.3). Respiratory gating had little effect on calculated parameters. CONCLUSION: ECG gating with the quadHIDAC can improve myocardial image quality in mice. This could have a major impact on the calculation of an image-derived input function for kinetic modelling.

Animals↗
PubMed2006

Quantification of subendocardial and subepicardial blood flow using 15O-labeled water and PET: experimental validation.

UNLABELLED: The purpose of this study was to assess the feasibility and accuracy of quantifying subendocardial and subepicardial myocardial blood flow (MBF) and the relative coronary flow reserves (CFR) using (15)O-labeled water (H(2)(15)O) and 3-dimensional-only PET. METHODS: Eight pigs were scanned with H(2)(15)O and (15)O-labeled carbon monoxide (C(15)O) after partially occluding the circumflex (n = 3) or the left anterior descending (n = 5) coronary artery, both at rest and during hyperemia induced by intravenous dipyridamole. Radioactive microspheres were injected during each of the H(2)(15)O scans. RESULTS: In a total of 256 paired measurements of MBF, ranging from 0.30 to 4.46 mL.g(-1).min(-1), microsphere and PET MBF were fairly well correlated. The mean difference between the 2 methods was -0.01 +/- 0.52 mL.g(-1).min(-1) with 95% of the differences lying between the limits of agreement of -1.02 and 1.01 mL.g(-1).min(-1). CFR was significantly reduced (P < 0.05) in the ischemic subendocardium (PET = 1.12 +/- 0.45; microspheres = 1.09 +/- 0.50; P = 0.86) and subepicardium (PET = 1.2 +/- 0.35; microspheres = 1.32 +/- 0.5; P = 0.39) in comparison with remote subendocardium (PET = 1.7 +/- 0.62; microspheres = 1.64 +/- 0.61; P = 0.68) and subepicardium (PET = 1.79 +/- 0.73; microspheres = 2.19 +/- 0.86; P = 0.06). CONCLUSION: Dynamic measurements using H(2)(15)O and a 3-dimensional-only PET tomograph allow regional estimates of the transmural distribution of MBF over a wide flow range, although transmural flow differences were underestimated because of the partial-volume effect. PET subendocardial and subepicardial CFR were in good agreement with the microsphere values.

Algorithms↗
PubMed2006

Accurate noninvasive measurement of infarct size in mice with high-resolution PET.

UNLABELLED: Reliable, repeatable, and time-efficient noninvasive measurement of infarct size in mice with PET would benefit studies aimed at the exploration of biochemical and functional changes associated with acute myocardial infarction (MI). PET with the radioactively labeled glucose derivative (18)F-FDG is used in humans to distinguish between viable but dysfunctional and nonviable myocardium. In this study, the feasibility, accuracy, and time efficiency of (18)F-FDG PET for quantification of infarct size in mice using a high-resolution animal PET device was evaluated in comparison with histomorphometry. METHODS: Mice were subjected to surgery with permanent ligation of the left anterior descending artery. PET was performed before and 7 d after surgery. The infarct size was determined from the PET studies using both manual and automated delineation. The second PET scan was followed by histomorphometric analysis. RESULTS: An excellent correlation between PET and histomorphometry was found for both manual (R = 0.98) and automated (R = 0.98) delineation, with linear regression curves close to unity (manual: y = 1.10x - 0.01; automated: y = 1.12x - 0.02). Automated analysis required <1 min per study. CONCLUSION: The measurement of infarct size in mice with (18)F-FDG PET is feasible and highly accurate. This noninvasive methodology permits unique longitudinal studies of biochemical parameters in mice and facilitates studies that aim to assess the effect of surgical and pharmacologic intervention after acute MI.

Algorithms↗
PubMed2005

[Scintigraphic molecular imaging].

Modern medicine is currently focusing its basic and clinical research towards "molecular medicine". This trend, together with the decoding of the human genome and the resulting design and use of transgenic mouse models of human diseases, demands that innovative imaging approaches are developed for man and mice. Non-invasive imaging modalities capable of quantifying molecular processes in vivo (collectively defined as "molecular imaging" techniques) are extremely interesting in this respect. This review focuses on the clinical and experimental scintigraphic molecular-imaging modalities SPECT and PET, and summarizes their actual and future impact in medicine.

Animals↗
PubMed2005

Monitoring left ventricular dilation in mice with PET.

UNLABELLED: Molecular imaging by small-animal PET is an important noninvasive means to phenotype transgenic mouse models in vivo. When investigating pathologies of the left ventricular (LV) myocardium, the serial assessment of LV volumes is important. By this, the presence of LV dilation as a sign of developing heart failure can be detected. Whereas PET is usually used to derive biochemical and molecular information, functional parameters such as ventricular volumes are generally measured using echocardiography or MRI. In this study, a novel method to monitor LV dilation in mice with PET is presented and evaluated using cardiac MRI. METHODS: A semiautomatic 3-dimensional algorithm was used to delineate the LV myocardial wall on static PET images depicting myocardial glucose metabolism ((18)F-FDG PET) for 20 mice: 10 wild-type and 10 genetically modified littermates designed to develop a dilative cardiomyopathy phenotype (cardiomyocyte-specific knockout of survivin). The volume enclosed by the 3-dimensional midmyocardial contour was calculated as a measure for LV volume for each mouse. Data were compared with ventricular volumes measured by MRI in the same animals. RESULTS: LV volumes obtained by PET and MRI correlated well (R = 0.89) for hearts with small and large left ventricles. In accordance with the hypothesis, the LV volumes were increased significantly for transgenic mice examined at an older age compared with those examined at a younger age (MRI: 160.5 +/- 25.7 microL vs. 114.7 +/- 15.2 microL [P = 0.012]; PET: 129.3 +/- 15.3 microL vs. 73.8 +/- 15.0 microL [P < 0.001], all values shown as mean +/- SD; for MRI, mean of end-diastolic and end-systolic volumes are given), whereas they did not for their wild-type littermates (MRI: 106.2 +/- 12.3 microL vs. 94.7 +/- 14.6 microL [P = 0.214]; PET: 82.6 +/- 20.9 microL vs. 65.0 +/- 16.9 microL [P = 0.185]). CONCLUSION: Evaluation and quantitation of LV dilation in both control and cardiomyopathic mice can be reliably and serially performed using small-animal PET and (18)F-FDG, yielding useful functional information in addition to metabolic data.

Aging↗
PubMed2004

Abnormal myocardial presynaptic norepinephrine recycling in patients with Brugada syndrome.

BACKGROUND: Life-threatening ventricular tachyarrhythmias can occur in young patients without structural heart disease (idiopathic forms). In many patients, these are typically triggered by an increased sympathetic tone, eg, by physical or mental stress. In contrast, in Brugada syndrome, ventricular tachyarrhythmias more often occur during rest or sleep when the vagal tone is predominant. Furthermore, adrenergic agonists can reduce the level of ST-segment elevation, whereas it is increased by parasympathetic agonists or adrenergic antagonists. The aim of this study was to investigate presynaptic and postsynaptic myocardial sympathetic function in patients with Brugada syndrome. METHODS AND RESULTS: Nine patients with Brugada syndrome (6 male, 3 female; age, 41+/-13 years) were enrolled in this study. The cardiac autonomic nervous system was assessed noninvasively, quantifying myocardial presynaptic and postsynaptic sympathetic function by means of positron emission tomography with the norepinephrine analogue 11C-Hydroxyephedrine (11C-HED) and the nonselective beta-blocker 11C-CGP 12177 (11C-CGP). Presynaptic sympathetic norepinephrine recycling, assessed by 11C-HED, was globally increased in patients with Brugada syndrome compared with a group of age-matched healthy control subjects (92.9+/-16.2 mL/g versus 69.1+/-14.2 mL/g; P<0.05), whereas postsynaptic beta-adrenoceptor density, assessed by 11C-CGP, was similar in patients and control subjects (10.4+/-6.7 pmol/g versus 10.2+/-2.9 pmol/g; P=NS). CONCLUSIONS: The present study on autonomic innervation in Brugada syndrome describes an enhanced presynaptic norepinephrine recycling with preserved beta-adrenoceptor density, further supporting the hypothesis of an autonomic dysfunction in Brugada syndrome. This is a further step toward the understanding of the pathophysiology of the disease with potential future impact on therapeutic strategies.

Adult↗
PubMed2004

Predictive cardiac motion modeling and correction with partial least squares regression.

Respiratory-induced cardiac deformation is a major problem for high-resolution cardiac imaging. This paper presents a new technique for predictive cardiac motion modeling and correction, which uses partial least squares regression to extract intrinsic relationships between three-dimensional (3-D) cardiac deformation due to respiration and multiple one-dimensional real-time measurable surface intensity traces at chest or abdomen. Despite the fact that these surface intensity traces can be strongly coupled with each other but poorly correlated with respiratory-induced cardiac deformation, we demonstrate how they can be used to accurately predict cardiac motion through the extraction of latent variables of both the input and output of the model. The proposed method allows cross-modality reconstruction of patient specific models for dense motion field prediction, which after initial modeling can be used for real-time prospective motion tracking or correction. Detailed numerical issues related to the technique are discussed and the effectiveness of the motion and deformation modeling is validated with 3-D magnetic resonance data sets acquired from ten asymptomatic subjects covering the entire respiratory range.

Algorithms↗
PubMed2004

Functional changes after partial left ventriculectomy and mitral valve repair assessed by gated perfusion SPECT.

UNLABELLED: A myocardial remodeling in dilated cardiomyopathy (DCM) after partial left ventriculectomy (PLV) has been previously discussed. The aim of this study was to investigate the functional changes in the follow-up of patients with DCM undergoing PLV using electrocardiographically triggered perfusion SPECT (gated SPECT). METHODS: Twelve DCM patients (10 men, 2 women; 56 +/- 9 y [mean +/- SD]), after successful PLV and mitral valve repair (PLV-MVR), were monitored by gated SPECT and echocardiography. Gated SPECT quantified end-diastolic volumes (EDV), end-systolic volumes (ESV), myocardial and scar volumes, as well as ejection fraction (EF) preoperatively, early (38 +/- 28 d), and late (296 +/- 130 d) after PLV-MVR. RESULTS: EDV and ESV showed an immediate reduction after PLV-MVR (EDV from 542 +/- 90 mL to 350 +/- 81 mL, P < 0.001; ESV from 452 +/- 91 mL to 254 +/- 79 mL, P < 0.001) with no significant change in the late follow-up (EDV late, 316 +/- 63 mL; ESV late, 207 +/- 63 mL; both P = not significant vs. early follow-up). PLV-MVR immediately improved EF (preoperative, 16.8% +/- 5.5%; early, 28.8% +/- 7.6%; P = 0.003) with no significant change in the late follow-up (36.0% +/- 9.4%; P = not significant vs. early follow-up). CONCLUSION: In this highly selected DCM patient group, gated perfusion SPECT assessed early responses in volumes and EF after PLV-MVR. However, although statistically nonsignificant in the small patient group, ESV and EDV were further decreased, whereas EF improved toward 1 y, coinciding with the improvement of clinical symptoms (New York Heart Association), potentially indicating a functional remodeling after PLV-MVR. Further studies in larger patient cohorts and longer follow-up are warranted.

Adult↗
PubMed2002

Assessment of infarct size by positron emission tomography and [18F]2-fluoro-2-deoxy-D-glucose: a new absolute threshold technique.

Along with hibernating myocardium, infarct size is a critical term in the progression of left ventricular remodelling and congestive heart failure. Both infarcted and hibernating myocardium determine changes in remote non-ischaemic tissue. This study was designed to test the accuracy of a new technique to quantify infarct size using positron emission tomography (PET) with [18F]2-fluoro-2-deoxy-D-glucose (FDG). Studies were carried out in (a) nine pigs with acute myocardial infarction (two sham-operated), produced by a 90-min occlusion of the circumflex coronary artery followed by a 4-h reperfusion, and (b) humans (six patients with ischaemic cardiomyopathy awaiting cardiac transplantation and five normal volunteers). In both animals and patients, myocardial FDG uptake was measured by PET during hyperinsulinaemic-euglycaemic clamp. Infarct size was quantified by an absolute threshold of tracer uptake obtained from the parametric (voxel-by-voxel) image of the metabolic rate of FDG. PET infarct size estimates were compared with independent ex vivo planimetric measurements of the explanted swine and patient hearts (at transplantation) after staining with triphenyltetrazolium chloride. There was good agreement between the planimetric and PET infarct size estimates both in pigs (n=9; r=0.96, v=0.94x+0.64, SEE=0.10, P<0.0001) and in humans (n=11; r=0.94, y=0.72x+2.93, SEE=0.09, P<0.0001). This study demonstrates the feasibility and accuracy of this PET method in estimating infarct size both in a model of reperfused acute myocardial infarction and in chronic ischaemic cardiomyopathy, although larger studies are needed to confirm these findings.

Animals↗